1. Field of the Invention
This invention relates to an aquarium pump for use both as an air pump and as a water pump for supplying air into water filled in an aquarium or for circulating the water, and further relates to an aquarium apparatus equipped with a passage aquarium which causes less operation noise and which enables an easy initial operation.
2. Description of the Related Art
It is a popular practice to keep ornamental fish in an aquarium, enjoying them as a part of an interior of a house or an office. An air pump is generally used for supplying air to water contained in the aquarium.
One example of this kind of conventional air pump is shown in FIG. 26. This air pump has a box-shaped main casing 100 with an opened bottom, an electromagnet 101 fixed to one of the opposing peripheral walls of the main casing 100, and a vibration arm 102 having one end fixed to the other opposing peripheral wall of the main casing 100. On the other end of the vibration arm 102, a permanent magnet 103 is attached so as to oppose to the core portion 101a of the electromagnet 101 at a close distance. A diaphragm 104 made of rubber is attached to a longitudinal central portion of the vibration arm 102. The diaphragm 104 is fitted onto a valve-housing 105 having an inlet opening 106a with an elastic inlet valve 108 and an outlet opening 106b with an elastic outlet valve 107. An inside of the diaphragm 104 communicates with an outlet port 109 which outwardly protrudes from the main casing 100 via the outlet valve 107, and also communicates with an inlet port 110 disposed in the main casing 100 via the inlet valve 108. The opened bottom of the main casing 100 is closed by a bottom wall (not shown).
When an alternating current passes through the electromagnet 101, the permanent magnet 103 begins to reciprocate in accordance with the alternating electromagnetic fields of the electromagnet 101 in the direction of the arrows shown in FIG. 26. This causes reciprocative movement of the vibration arm 102, which in turn causes a repetition of expansion and compression of the diaphragm 104. When the diaphragm 104 is compressed, the outlet valve 107 opens to send air confined in the diaphragm 104 out of the main casing 100 through the outlet port 109. On the other hand, when the diaphragm 104 is expanded, the outlet valve 107 closes and the inlet valve 108 opens to introduce air into the diaphragm 104 through the inlet port 110 disposed in the main casing 100. In accordance with the repetition of expansion and compression of the diaphragm 104, air is supplied to an aquarium through the outlet port 109.
In the conventional air pump, the inlet port 110 is disposed inside the main casing 100 because, if the inlet port 110 is provided outside the main casing 100, noise generated by the pump will directly leak through the inlet port 110.
In addition, various aquariums equipped with a passage aquarium portion through which fish can come and go freely have been proposed because such a passage aquarium portion can enhance the ornamental effect of the aquarium. For example, Japanese Utility Model Laid-open Publication No. 58-105870 discloses an aquarium that is divided into two separate aquarium portions by a central partition, and an inverted generally U-shaped passage aquarium portion having opposite end openings is disposed above the aquarium. Each of the opposite end openings of the passage aquarium portion is disposed in the water contained in a respective one of the separate aquarium portions with water filled in the passage aquarium portion so that fish can freely pass through the passage aquarium portion. Furthermore, a water pump driven by an electric motor is used so as to suck water from one of the separate aquarium portions via an inlet pipe and so as to send out the sucked water to the other separate aquarium portion via an outlet pipe. Thus, the water filled in the two separate aquarium portions can be circulated through the passage aquarium portion.
However, in the aforementioned aquarium equipped with a passage aquarium portion, since a water pump driven by an electric motor is used, the noise caused by the motor and/or the water pump is loud. Thus, the noise can be undesirably loud when the aquarium is placed in a quiet environment such as in a quiet room or office. Especially, at nighttime, the noise is augmented because the environment is quieter, which may make the user more uncomfortable, deteriorating the user's concentration, or even disturbing the user's sleep. Thus, the level of noise may sometimes go beyond the user's endurance range. As a result, it is strongly required to lower the noise level during the operation of the water pump.
Also, in the aforementioned aquarium equipped with a passage aquarium portion, water must be filled in the passage aquarium portion by sucking air from the passage aquarium portion before operating the water pump. This requires time and troublesome initial operation of the system. Accordingly, it is necessary to establish a new system which is simple in initial operation.